I wrote the first version of rgba.php as a complement to an article on RGBA that I posted on Februrary 2009.
Many people seemed to like the idea and started using it. With their valuable input, I made many changes and released v.1.1 (1.1.1 shortly after I posted the article due to another little fix) on October 2009.
More than a year after, quite a lot of people still ask me about it and use it, so I decided to make a github repo for it and release a new version, with a much easier to use syntax for the URL, which lets you just copy and paste the color instead of rewriting it:
background: url('rgba.php/rgba(255, 255, 255, 0.3)'); background: rgba(255, 255, 255, 0.3);
background: url('rgba.php?r=255&g=255&b=255&a=30'); background: rgba(255, 255, 255, 0.3);
I also made a quick about/demo page for it.